The present invention is directed to polyblends of (a) high performance polyvinyl chloride resins, (b) high molecular weight non-equimolar copolymers of ethylenically unsaturated dicarboxylic acids, or their derivatives, and at least one copolymerizable monomer, and (c) certain copolymers which serve to interface with the other two ingredients.
Polyvinyl chloride, in addition to being relatively inexpensive, is a polymer which can be easily modified to obtain an excellent balance of physical properties. The polymer is inherently flame retardant and has outstanding chemical resistance. The primary deficiency of polyvinyl chloride is its poor heat resistance. Another deficiency is the inability to accept paint on its surface.
U.S. Pat. No. 3,626,033 teaches to overcome the brittleness and low temperature deformation of polyvinyl chloride by blending the polyvinyl chloride with a polydiene rubber nitrile graft copolymer and an anhydride containing copolymer such as a styrene/maleic anhydride copolymer.
U.S. Pat. No. 4,311,806 teaches to blend rubber-modified styrene/maleic anhydride copolymers into polyvinyl chloride. These binary blends had better heat distortion temperatures but lower impact properties. The blends may also contain a rubber modifed styrene/acrylonitrile copolymer. The ternary blends had improved heat distortion temperature with increased impact properties.
U.S. Pat. No. 4,339,554 teaches to blend styrene/maleic anhydride copolymer into polyvinyl chloride in order to increase the heat distortion temperature. U.S. Pat. No. 4,371,666 also teaches this blend and points out that blends with at least 40% polyvinyl chloride are flame retardant.
U.S. Pat. No. 4,469,844 and U.S. Pat. No. 4,469,845 teach to blend both styrene/maleic anhydride copolymers and rubber-modified styrene/maleic anhydride copolymers with rubber-modified polyvinyl chloride. These blends had increased impact properties but had lower heat distortion temperatures than the polyvinyl chloride alone.